Please update to mSecure 5.5.3 if still using mSecure 5.5.2 instead of following these steps.

mSecure 5.5.2 Crashing or will not start.

This issue seems to affect those updating from mSecure 5.x to mSecure 5.5.2. Please make sure you have access to your mSecure 5 information on another device or that you have set up either mSecure Cloud, iCloud, or Dropbox syncing before following the steps below. Also, make sure to have access to your QR code or authentication email:

The QR code/authentication should not be required if you have already authenticated your account with mSecure 5.5 on iOS or Mac. However, it's always good to have access to the QR code. 

To fix your crashing issues:

  1. Quit mSecure on your Mac
  2. Open a Finder window and using the menus at the top, select the ‘Go’ -> ‘Go to Folder…’
  3. Enter
    ~/Library/Containers/com.mseven.msecuremac/Data/Library/Application Support/mSecure
  4. Click ‘Go’
  5. Move the mSecure.mscb file to the trash
  6. Re-launch mSecure
  7.  Sign in to your account

We believe we have found the issue and have fixed the issue internally. A fix will be available in our next Mac update.